During land colonization one of the major modifications in plant body is the formation of roots, organs specialized in water and nutrient uptake. Roots have evolved an extraordinary variety of different structures enabling them to adapt to different soils and conditions. The root cortex is a clear example of this interspecific variability. Thanks to secondary growth of the cortex, plants can control air quantity when growing on wet soils, and store nutrients (starch) when growing in adverse weather and nutritive conditions. Utilizing a comparative development approach between Arabidopsis thaliana, one cortex, and its close relative Cardamine hirsuta, two cortexes, it has been shown that a differential cellular distribution of microRNA165 and microRNA166 (miR165 and 166) and its target PHABULOSA (PHB), a member of the HD-ZIPIII transcription factor family, is at the basis of cortical patterning diversity. The goal of my project is to acquire deep knowledge on the different distribution of miR165 and 166 and to identify the molecular mechanisms that drive the different distribution of miR165 and 166 between Arabidopsis and Cardamine. We identified diverse transcription factors that drive the differential expression of these miRNAs and we show that these transcription factors are responsible cortex patterning variability between the two species. This data will shed light on the developmental conserved mechanisms structuring cortex tissue patterning.